# Why Is My Guinea Pig Not Eating Hay? Causes and Fixes A guinea pig that stops eating hay is usually telling you something is wrong. Hay is the main food in a guinea pig's diet, so refusing it often points to dental pain, digestive slowdown, or another health problem that needs attention [1]. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Hay should be available at all times and should make up the bulk of your guinea pig's diet, not a side dish [1]. - The two most common reasons for hay refusal are dental disease (overgrown or misaligned teeth) and a slow or painful gut [2]. - A guinea pig that stops eating anything, drools, or sits hunched is an emergency. Call a vet the same day [2]. - Weigh your guinea pig weekly. Weight loss is often the first sign you can measure at home. - Never wait a few days to "see if it improves." Guinea pigs decline fast when they stop eating. ## What Hay Refusal Looks Like and What Is Normal A healthy guinea pig eats hay throughout the day and night. Hay wears down teeth that grow continuously and supplies the fiber that keeps the gut moving [1]. Normal output follows normal input, so a guinea pig eating well should also be passing well-formed droppings. Signs that hay intake has dropped include: - Hay left untouched in the rack for many hours - Smaller or fewer droppings - Picking at pellets or greens but ignoring hay - Drooling, dropping food, or chewing on one side - Weight loss, a rough coat, or less activity Some owners notice the opposite pattern. If your guinea pig is only eating hay and refusing everything else, that still matters, because it can mean pellets or vegetables are causing mouth pain or digestive upset. If your guinea pig is not eating veggies but eating hay, the hay habit is a good sign, but the refusal of other foods still deserves a vet visit. ## Why Is My Guinea Pig Not Eating Hay? Main Causes | Cause | Typical clues | How urgent | |---|---|---| | Dental disease (malocclusion, overgrown molars) | Drooling, dropping food, weight loss, mouth bleeding, nasal or eye discharge | Urgent, see a vet quickly [2] | | Vitamin C deficiency (scurvy) | Rough coat, lameness, swollen joints, appetite loss, diarrhea | Urgent, needs treatment [3] | | Gut slowdown or stasis | Few or no droppings, hunched posture, belly pain, no interest in food | Emergency | | Pain elsewhere (injury, fracture, urinary or reproductive issues) | Reluctance to move, abnormal posture, crying when handled | Urgent [4][5] | | Infection or parasites | Diarrhea, weight loss, eye or nose discharge, multiple animals affected | Urgent, some are contagious to people [6] | | Stress or environment change | New cage, new companion, loud household, dirty hay | Try fixes first, then call a vet | | Poor-quality or stale hay | Hay smells musty, dusty, or moldy, or has been sitting for weeks | Replace hay, monitor closely | ### Dental Disease Guinea pig teeth grow continuously. When the upper and lower teeth do not line up, a condition called malocclusion, the teeth overgrow, develop sharp edges, and cause pain while chewing [2]. Causes include genetics, not enough hay chewing, and vitamin C deficiency [2]. Dental disease can lead to drooling, weight loss, mouth bleeding, tooth root abscesses, and discharge from the nose or eyes [2]. The tricky part is that the molars at the back of the mouth often cause the problem even when the front teeth look fine [2]. That is why a vet needs to look inside the mouth, sometimes with skull x-rays, and may need to trim or file the teeth [2]. Chronic cases can need repeated dental trimming every month [2]. Some guinea pigs develop macrodontia (enlarged tooth roots) or odontogenic abscesses, and surgery on the upper molar teeth is sometimes required [7]. This is advanced care, so ask your vet what is appropriate for your pet. ### Vitamin C Deficiency Guinea pigs cannot make their own vitamin C, so they must get it from food [3]. Without enough, they can lose their appetite, develop dental problems, have swollen joints, bleed under the skin, become weak, and possibly die [3]. Signs include a rough coat, lameness, weight loss, diarrhea, and sudden illness [3]. Vitamin C in pellets is unstable and breaks down with heat, light, and moisture, so a bag that has sat for months may not deliver what the label promises [3]. Guinea pigs need at least 10 mg of vitamin C per kg of body weight per day, and pregnant females need 30 mg per kg per day [3]. Because most guinea pigs weigh around 1 kg, giving 10 mg per guinea pig daily is safe, and 30 mg is safe for a pregnant female [3]. Ask your vet before adding any supplement. ### Gut Slowdown and Stasis Fiber from hay keeps the digestive tract moving [1]. When hay intake drops, the gut can slow down, gas builds up, and the guinea pig feels worse, which makes it eat even less. This cycle can become life threatening within a day or two. Watch for fewer droppings, no droppings, a hunched posture, teeth grinding, or a belly that feels tight or painful. Abdominal pain and loss of appetite can also signal serious problems such as a mesenteric torsion, a twisted bowel that has been reported in guinea pigs and requires surgery [8]. Do not try to treat gut stasis at home with home remedies. Call your vet. ### Pain, Injury, and Other Medical Problems A guinea pig with a fractured jaw or a painful tooth may stop eating because chewing hurts [5]. Urinary or reproductive problems can also cause anorexia and a painful posture, and these sometimes require surgery [4]. Infectious causes such as Chlamydia caviae and Cryptosporidium wrairi can cause appetite loss, weight loss, diarrhea, and even death in a herd, and both can spread to people [6]. If you have multiple guinea pigs and more than one is sick, tell your vet right away. ### Stress and Husbandry Problems Sometimes the answer is simpler. A new cage mate, a recent move, a noisy room, or a dirty hay rack can put a guinea pig off its food. Hay that is dusty, musty, or moldy will also be refused. Offer hay in a rack to keep it clean and dry, and replace it daily [1]. ## Red Flags That Make It an Emergency Call an emergency veterinary clinic right away if your guinea pig: - Has not eaten anything for 12 hours or more - Has no droppings, or very few, for 12 hours or more - Is drooling heavily or has food stuck around the mouth [2] - Sits hunched, grinds its teeth, or cries when touched - Is breathing fast, weak, or unable to stand - Has a swollen or painful belly - Has diarrhea, especially with weight loss or multiple animals affected [6] Guinea pigs are small prey animals. They hide illness well and can crash quickly. When in doubt, call. If you are comparing symptoms across species, our guide to [Why Is My Dog Not Eating?](/knowledge/veterinary-medicine/symptom-guides/why-is-my-dog-not-eating) explains how appetite loss works in dogs, but guinea pigs need faster action. ## Safe Things You Can Do at Home While Waiting for the Vet These steps buy time. They do not replace a diagnosis. - **Keep hay available at all times.** Offer fresh, good-quality grass hay such as timothy or orchard grass in a clean rack [1]. - **Try a fresh, high-quality batch.** Hay that has been open for weeks loses its appeal. A new bag from a different batch may tempt your guinea pig. - **Offer a variety of hay types.** Timothy and orchard grass are both fine choices [1]. Some guinea pigs prefer one texture over another. - **Check the water bottle.** A stuck valve or dirty bottle can reduce drinking, which reduces eating. - **Offer small amounts of safe greens.** Leafy greens such as romaine, green leaf lettuce, and carrot tops are popular [1]. Avoid iceberg lettuce because it is mostly water, and limit high-calcium greens like parsley, kale, and spinach because excess calcium may contribute to bladder stones [1]. - **Keep treats tiny.** Small pieces of carrot, apple, or pear are fine as occasional treats, but fruit is high in sugar and can cause digestive upset if overfed [1]. Remove uneaten fresh food after a few hours [1]. - **Do not force-feed unless your vet tells you to.** Improper feeding can cause choking or aspiration. - **Weigh your guinea pig daily** during a problem and write down the numbers. - **Reduce stress.** Keep the room quiet, avoid handling more than needed, and keep the cage clean. If your guinea pig is eating hay but refusing vegetables, review what is safe with our guide to [What Guinea Pigs Can and Cannot Eat](/knowledge/veterinary-medicine/small-mammal-care/guinea-pig-diet) and [Guinea Pig Diet Food](/knowledge/veterinary-medicine/nutrition/guinea-pig-diet-food). ## What Your Veterinarian Will Check and Test Your vet will start with a full physical exam, including a careful look at the mouth. Because back molars are hard to see, sedation or anesthesia may be needed for a complete oral exam [2]. Skull x-rays can help assess the teeth and tooth roots [2]. Other tests may include: - **Weight and body condition scoring** - **Abdominal palpation and imaging** to look for gas, blockage, or masses [8][4] - **Blood work** to check organ function and look for signs of infection or deficiency - **Fecal testing** if diarrhea or parasites are suspected [6] - **Dental trimming or filing** if teeth are overgrown [2] Treatment depends on the cause. Dental disease may need trimming, filing, or in some cases surgery on tooth roots [2][7]. A fractured jaw may be managed with a chin sling and nutritional support [5]. Infections need specific treatment, and some, like Chlamydia caviae and Cryptosporidium wrairi, can spread to people, so tell your vet about any human illness in the home [6]. Your vet will calculate any medication dose from your pet's weight and health. ## Prevention and Daily Monitoring Prevention is mostly about hay, vitamin C, and early detection. - **Make hay the main food.** Offer a measured amount of pellets (about 2 tablespoons daily) and unlimited grass hay [1]. - **Use a hay rack** to keep hay clean and dry, and refresh it daily [1]. - **Protect vitamin C.** Pellets lose vitamin C over time, so check freshness and ask your vet about supplementation [3]. - **Weigh weekly.** A kitchen scale is one of the best tools you own. - **Watch droppings.** They are a daily report card on gut health. - **Schedule dental checks.** Guinea pigs with a history of dental disease may need regular trimming [2]. - **Keep the cage clean and the room calm.** - **Quarantine new guinea pigs** before introducing them to your herd, since infections can spread quickly [6]. If you notice a pattern of appetite changes in another pet, our article on [Dog Not Pooping but Eating Normally: Causes and Solutions](/knowledge/veterinary-medicine/digestive-and-urinary-care/dog-not-pooping-eating-normally) covers a similar digestive warning sign in dogs. For reptiles, see [Why Is My Snake Not Eating? Causes and Solutions](/knowledge/veterinary-medicine/reptile-care/snake-not-eating). ## Limitations and When to Contact a Veterinarian This article cannot tell you what is wrong with your individual guinea pig. Only a veterinarian who examines your pet can do that. Contact a veterinarian the same day if your guinea pig has stopped eating hay, is losing weight, or is drooling [2]. Go to an emergency clinic immediately if there is no eating or no droppings for 12 hours, if your guinea pig is hunched or unresponsive, or if it has a painful or swollen belly. Schedule a routine visit if you notice a slow decline in hay intake over several days, even if your guinea pig still seems bright. Early dental and nutritional problems are much easier to manage than advanced ones [3][2]. ## Frequently Asked Questions ### Why is my guinea pig only eating hay? If hay is the only food your guinea pig will eat, the hay habit is good, but the refusal of pellets and vegetables still needs attention. Mouth pain, vitamin C deficiency, or a digestive problem can make other foods uncomfortable to eat [3][2]. Offer fresh hay, check the water bottle, and call your vet if the pattern lasts more than a day. ### My guinea pig is not eating veggies but eating hay. Should I worry? Yes, a little. Eating hay means the gut is still moving, which is reassuring, but refusing vegetables can be an early sign of dental pain or another problem. Watch for drooling, weight loss, and changes in droppings. If the refusal lasts more than 24 hours or comes with other signs, see your vet. ### How long can a guinea pig go without hay? Not long. Guinea pigs need constant fiber to keep the gut moving, and hay should be available at all times [1]. A guinea pig that has eaten nothing for 12 hours or has no droppings for 12 hours needs emergency care. Do not wait to see if it improves on its own. ### Can I just give more pellets if my guinea pig won't eat hay? No. Pellets are only a small part of the diet, about 2 tablespoons daily, and they do not replace the fiber and tooth wear that hay provides [1]. Offering extra pellets can also mask the problem and lead to weight gain without fixing the cause. Keep hay available and find out why your guinea pig is refusing it. ### What if my guinea pig won't eat hay but acts normal? Acting normal does not rule out a problem, because guinea pigs hide illness well. Weigh your guinea pig and check its droppings. If weight is stable and droppings look normal, try fresh hay and reduce stress. If weight drops or the refusal continues past a day, call your vet. ## Related Articles - [What Guinea Pigs Can and Cannot Eat](/knowledge/veterinary-medicine/small-mammal-care/guinea-pig-diet) - [Guinea Pig Diet Food](/knowledge/veterinary-medicine/nutrition/guinea-pig-diet-food) - [Guinea Pig Respiratory Infections: Causes, Signs, and Treatment](/knowledge/veterinary-medicine/small-mammal-care/guinea-pig-respiratory-infections-causes-signs-treatment) - [Guinea Pig Not Eating or Drinking: What to Do](/knowledge/veterinary-medicine/small-mammal-care/guinea-pig-not-eating-or-drinking) - [Guinea Pig Not Eating and Hiding: What It Means](/knowledge/veterinary-medicine/small-mammal-care/guinea-pig-not-eating-hiding) ## References 1. [Diet for a Guinea Pig - All Other Pets](https://www.merckvetmanual.com/all-other-pets/guinea-pigs/diet-for-a-guinea-pig). Merck Veterinary Manual. 2. [Common Health Problems of Guinea Pigs - All Other Pets](https://www.merckvetmanual.com/all-other-pets/guinea-pigs/common-health-problems-of-guinea-pigs). Merck Veterinary Manual. 3. [Nutritional Problems of Guinea Pigs - All Other Pets](https://www.merckvetmanual.com/all-other-pets/guinea-pigs/nutritional-problems-of-guinea-pigs). Merck Veterinary Manual. 4. [Radiographic and ultrasonographic findings of seminal vesiculitis with nonmineral stones in a guinea pig: Case report](https://pubmed.ncbi.nlm.nih.gov/39476219/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2025. 5. [Use of chin sling for conservative treatment of mandibular fracture in a guinea pig (Cavia porcellus)](https://pubmed.ncbi.nlm.nih.gov/37451679/). Journal of the American Veterinary Medical Association, 2023. 6. [Zoonotic potential of guinea pigs: Outbreak of cryptosporidiosis combined with chlamydiosis in a breeding guinea pig herd](https://pubmed.ncbi.nlm.nih.gov/36562747/). Schweizer Archiv fur Tierheilkunde, 2023. 7. [Ventral Transorbital Apicoectomy of the Maxillary Second and Third Molar Teeth in Guinea Pigs (Cavia porcellus): 26 Cases](https://pubmed.ncbi.nlm.nih.gov/41600709/). Veterinary sciences, 2026. 8. [Radiographic and Ultrasonographic Findings of a Segmental Mesenteric and Jejunal Torsion in a Guinea Pig](https://pubmed.ncbi.nlm.nih.gov/40365910/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2025. ## Further Reading - [Merck Veterinary Manual: Guinea Pigs](https://www.merckvetmanual.com/all-other-pets/guinea-pigs)